A function of superposing an image on a screen of a TV image display apparatus to display information with regard to, for example, a channel number, a menu, input switching or the like separately from an inherent TV image (original image) is known as on-screen display (hereinafter, referred to as OSD).
OSD is realized by superposing a display signal from a microcomputer or the like on RGB signals. As one method of OSD, there is known a constitution of displaying a certain designated region on a screen in a uniform color and arranging information displayed by OSD (OSD information) in the designated region by constituting a background thereby. Further, as other method of OSD, OSD is displayed at a designated region through an original image as a background. Further, according to OSD by the transparent display, in order to facilitate seeing OSD information on a screen, the original image at the designated region can be displayed by a half tone display.
As half tone formation in a transparent display of a background art, respective component colors constituting an original image, that is, original image signals of R, G, B respectively are uniformly attenuated at a designated region. Further, in recent years, there is also a case in which by adjusting relative intensities thereof while attenuating original image signals of respective colors of RGB, a half tone display (referred to as a color half tone display) for providing a specific hue to the region is carried out while displaying an original image by a transparent display at a designated region.
According to the color half tone display of the background art, there is a problem in that as a result of changing a balance of RGB of the original image signals constituting a background, depending on a color of the original image or an arrangement thereof, a strange feeling may be given to a person viewing the screen.